Be that as it may, I have a couple of further queries, I think I know the answers but I want to be quite sure:-
The new CU will simply have a main switch and all RCBO circuits, that's OK isn't it? We are TT and there is a 100mA time delayed RCD immediately after the company fuse in the garage. This feeds an 'outdoors' CU in the garage and, through a further fuse, the house CU via an underground cable.
I think I'll need to extend the incoming feed to the new house CU, what's the best way to do this. I guess a Henley Block is the obvious easy way, are there any alternatives? I could possibly solder and sleeve with heatshrink or I do have a hydraulic crimp tool so could get tube crimps and do it that way. Are there any special rules for incomers?